Dental chair



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DENTAL @EMBA Patentd Apr. 27, 1897.

Las Jz/y,

(No Model.) Y Y 9 Sheets-Sheet 3.

B. M. WILKERSON.

DENTAL CHAIR.

(No Model.) 9 Sheets-Sheet 4. B. M. WILKERSON.

DENTAL CHAIR.

No. 581,670. Patented Apr. 27, 1897.

www@ (No Model.) 9Sheets Sheet.

B. M, WILKERSON.

DENTAL CHAIR.

Patented Apr. 27, 1897.

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(No Model.) asheets-sheet e.

B. M. WILKERSON.

DENTAL CHAIR.

Patented Apr. 27, 1897.

No. 58L670.

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(No Model.) 9 Sheets-Sheet 8.

B. M. WILKERSON.

DENTAL CHAIR.

No. 581.670. Patented Apr. 27, 1897.

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(No Model.) QSheets-Sheet 9. B. M. WILKERSON. DENTAL CHAIR.

No. 581,670. Patented Apr. 27, 1897.

devices.

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BASIL M. VILKERSON, OF BALTIMORE, MARYLAND.

DENTAL CHAIR.

SPECIFICATION forming part of Letters Patent No. 581,670, dated April27, 1897'. Application filed January '7, 1895. Serial No. 534,105. (Nomodel.)

To all whom it 11i/fr 1/ (2o/warn.:

Be it known that I, BAsIL M. WILKnRsoN, a citizen of the United States,and a resident of Baltimore, in the State of Maryland, have inventedcertain new and useful Improvements in Dental Chairs, of which thefollowing is a specification.

My invention has relation to means `for elevating, lowering, andadjusting the seat of the chair; to the means for adjusting thefoot-board, the back, and the head-rest; to providing the foot-boardwith a folding step which automatically assumes its position of use whenthe foot-board occupies an elevated position, and to combining with thebody of the chair an arm-rest detachable at will therefrom and also sojoined thereto that it may be turned forward and down out of the waywhen ever desired.

The nature ot my improvements and the manner in which they are or may becarried into practical effect can best be explained and understood byreference to the accompanying drawings, in which- Figure l is a sideelevation of a dental chair embodying my improvements in their preferredform. Fig. 2 is a plan, on enlarged scale, of the chair-base with thepivot of the elevating-lever in section. Fig. 3 is a section on line 33, Fig. 2. Fig. 4E is a section of the chair-base on line -t t, Fig. 5.Fig. 5 is a section on line 5 5, Fig. 4l. Fig. 6 is a section on line Gt', Fig. Fig. 7 is a detail section on line 7 7, Fig. 5, intended toillustrate the valve arrangement for regulating the flow of the liquidto and from the plu nger-cylinder. Fig. 8 is a section illustrative ofthe device for opening the valve which permits the liquid to pass outfrom the plunger-cylinder when it is desired to allow the plunger todescend. Fig. 9 is a side elevation, partly in section, of thechair-base, designed more particularly to illustrate the plunger lockingand releasing In this figure l have shown in section the ball member ofthe ball-and-socket chair-supporting joint attached to the plunger andprovided with a socketed bracket for carrying a spittoon and otherappurtenances. Fig. 10 is a perspective view of the upper part of thebase. Fig. 11 is a considerably-enlarged perspective view of a portionof the plunger locking and releasing devices. Fig. l2 is a plan of thechair with the seat and a portion of the back frame removed. Fig. 13 isa longitudinal vertical central section of the chair with the headrestcarrier in elevation. Fig. 14 is a section of the two members of theball-and-socket joint on line 14 14 of Fig. 12. Fig. 15 is a partialsection on line 15 l5, Fig. 14k. Fig. 1d is a section of the `foot-boardof the chair on line 1G i6, Fig. l2, showing the folding step for use ingetting into or out of the chair when the latter is in elevatedposition. Fig. 17 is a sectional view, on enlarged scale, of a portionof the foot-board, one of its hinged supporting-brackets, an d thelocking mechanism for holding the latter in adjusted position. Fig. 17fLis an enlarged cross-section on line 17, Fig. 17, of the upper end ofthe locking-pawl and of the rack-bar, which it engages. Fig. 1S is ahorizontal section of part of the rear cross-bar of the foot-board frameand a sectional elevation of a portion of one of the adjusting-barsconnected thereto. Fig. 19 is a sectional side elevation of part of oneot' the arm-rests and the portion of the chair-frame to which it isattached. Fig. 20 is a rear elevation ot' the chair-back. Fig. 21 is avertical central section of the same on line 2l 2l, Fig. 20. Fig. 2ln isa View ot' the toggle-lever by which the difterent joints ot thehead-rest carrier are locked. Fig. 22 is an elevation of the back-padframe. Fig. 23 is a section on line 23 23, Fig. 2l. Fig. 24 is a sectionon line 2a 24, Fig. 21. Fig. 25 is a section on line 25 25, Fig. 20,through the handle which controls the locking devices Vfor theback-frame. Fig. 26 is a section on line 26 26, Fig. 2l. Fig. 27 is anenlarged sectional plan of the device by which the back-pad is adjustedand held at different inclinations relatively to the backframe. Fig. 28is a top View of the headrest. Fig. 29 is an enlarged section on line 2929, Fig. 21, through one ofthe side bars of the back-frame, showing thespring-pressed friction -pad for preventing too-rapid drop of that framewhen the latter is released. Fig. 30 is an enlarged section of thepivoted bayonet-joint between the arm-rest, Fig. 19, and its frame. Fig.81 is a perspective View of the male member of the joint. Fig. 32 is anenlarged perspective view of the cam and IOO finger shown in Figs. 0 andl0 for t-ripping the releasing-valve and plunger-clamping mechw anism.Fig. is a sectional view of a modification which will be hereinaftermore particularly referred to.

Chair-Elec citing Meehan-tsm.

It is my object to impart immediate and continuous upward movement tothe chairbody while applying the power which produces that movementintermittently and through the medium of a foot-lever-operatedstep-by-st-ep movement.

A further object is to obtain a dental chair having an extensivevertical range of movement and capable of being rigidly locked at anypoint in said range. This portion of my improvements is illustrated inFigs. l to ll, inclusive, and in Fig. 32. The chair is one having ahydraulic lift comprising a plunger which supports the chair-body, aplunger-cylinder, a pump, and a reservoir from which the pump draws theliquid which is to be forced into the plunger-cylinder for the purposeof lifting the plunger, the pump being operated byafoot-lever, ascustomary.

A is the base, which constitutes also the liquid-reservoir, the liquidemployed. being usually oil. It sets and can rotate in the pedestal Band contains the pump C and its connections, as well as theplunger-cylinder D, in which is contained the chair-body-support-ingplunger. A suitable lock can bc provided to hold, when desired, the basefrom rotating in the pedestal. The rod of the pump-piston C has, asindicated in Fig. 4f, a forked upper end c, which is entered by a pin con an arm c2, fast on the pivot of and vibrating with the foot-lever C2,Fig. l. The depression of the lever gives the downstroke to thepiston-the stroke which forces the oil from the pump into theplunger-cylinder. The upstroke is occasioned by the spring c3,surrounding the piston-rod and confined between the head of thepump-cylinder and a washer c4 on the rod, which spring is compressed onthe downstroke. The check-valve controlling the oil-inlet from thereservoir is shown at ci and the outlet check-valve for preventingbackiiow from the plunger-cylinder is shownat c, Fig. it, this valvebeing interposed in the passage c7, between the pump and the plungercylinder, the liquid entering the latter cylinder at the point es, Figs.3, 4, and 5, and passing down to the under side of the plunger through aclearance d, Fig. 3, provided for that purpose between the plunger andthe cylinder D.

Under the arrangement thus far described the upward movement of theplunger would be intermittent and step by step, responding only to thedown movement of the foot-lever. To make that intermittent movementimmediately continuous, I provide a pressure-storage chamber C3, whichcommunicates with the passage c'I on the side of the check-valve cG nextto the plunger-cylinder. This chamber contains a piston-diaphragm ormovable head C5, which by the pressure of the oil forced in by the pumpis forced up in that chamber and is influenced also by a strong springCG, (or its mechanical equivalent, such as a weight,) which tends toforce the head in a direction opposite to that in which it is moved bythe hydraulic pressure. I have thus in effect a pressure-storage chamberwhose capacity is made variable by means of a movable bulkhead orpartition influenced in one direction by the pump and in the otherdirection by a spring or its equivalent. It is to be observed also thatthe inlet e8 to the plunger-cylinder is smaller in cross-sectional areathan the passage cl. Under this arrangement at each stroke of the pumpthe oil will not only be forced into the plunger-cylinder to lift theplunger, but the pressure-storage piston C5 will be forced back into itschamber C3, thus com pressing the spring. Then after the stroke of thepump has been delivered the spring C takes up the work instantly and byits recoil continues to force the oil into the plungercylinder while thepump-piston and its operating foot-lever are on the upstroke. In thisway the upward movement of the plunger from the start is madecontinuous.

I am aware, of course, that pumps have been provided with air-chambersfor the purpose of equalizin g the flow; but such a device would beunfitted for the purposes which I have in view. The chair in such eventwould not respend immediately to the movement of the foot-lever; norwhen once in movement would that movement be at once continuous. In thepassage c7, at a point near to the inlet to the plunger-cylinder, isstill another checkvalve c, Fig. 7, to prevent the weight carried by theplunger from affecting the piston C5. The return-passage from theplunger-cylinder back into the oil-reservoir is shown at 010, Fig. 7. Itis controlled by a valve c, which when tripped or lifted permits theliquid from the plunger-cylinder to flow hack into the oil-reservoir A.The device for the purpose consists of a vertically-movable rod cl2,Figs. 4t and 8, having at its lower end a toe orlateral projection cl3,that comes under the stem of the valve cu. This rod at its upper endpasses out through the top of the oil-chamber, is su pported in a fixedguide-bracket c, and hasa spring C15, which normally holds it down inposition where the valve c11 will not be. lifted. The spring c for thispurpose is confined between the fixed guide-bracket c and a flange orshelf om, fast to the rod.

It will be remarked that the pump, the

pressure-storage chamber, and all valves and connections are comprisedin one organism, as shown clearly in Figs. et and 5, the connection ofpipe cT to the plunger-cylinder inlet being' made by means of a nipplewhich fits into the inlet-opening in that cylinder. These devices thusare removable in one piece or as a whole from the oil-reservoir forexamination and possible repairs or cleaning which ICO IIO

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may be necessary. It is for this purpose that I make the joint c cbetween the pump-piston and its operating-arm c2 of such character thatthe two can readily be disengaged whenever desired, and the top or domeof the oil-reservoir for the same purpose is made so that it or so muchof it as is over the pressure-storage chamber and pump and connectionscan be taken off to uncover said parts and permit them to be lifted outfrom the oilreservoir. The nipple end of the passage cT can readily bedisengaged from the inlet-opening cs, in which it iits, by tilting alittle the pump in a direction to withdraw the nipple from the opening.The pump-casting and its connections are held down tight in place whenin the base or oil-reservoir in any suitable way-as, for example, by across-bar and pressure-screw used as like devices are employed to holdcovers upon fruit-jars.

General reference only has thus far been made to the plunger, theimprovements already described, as well as others hereinafter described,being applicable to Various kinds of plungers or vertically-movablechair-supporting bars or stems; but the plunger shown in the drawings,both in itself and in its ad juncts, possesses peculiar characteristicswhich give it extensive range of movement and permit it to be rigidlylocked at any point throughout that range.

The plunger itself is telescopic in structure, consisting in thisinstance of two members E F. The outer member E is tubular. Above theclearance CZ it lits the plunger-cylinder closely, and the joint betweenthe two is packed at- CZX. The inner member F its and is movable up anddown in the outer member E and has its lower end packed like a piston,as at f, and upon it is placed the chairbody.

The oil when [ii-st admitted to the plungercylinder raises both membersas one until the outer tubular member reaches its upward limit andstops. Then the inner member (provided, of course, the pumping action iscontinued) alone rises, moving up in the now stationary tubular outermember until it, too, has reached its upward limitof motion or until thechair-body has been raised within that limit to the desired height. Inthis way I obtain a high-low chair in which all parts are contained in abase which may be wholly above the floor instead of having theplungercylinder extending partly below the floor, as heretofore usuallyhas been the case, owing to Jthe fact that the plunger has been made ofa single continuous piece.

Various means for limiting the upward movement of each member obviouslymay be employed. That l prefer for the purpose so far as concerns theouter member E is to connect it at its upper end to a vertical bar c,which is held between and can move up and down between guide-.flanges e'in a seat upon the exterior of the base. From the inner face of the barprojects a stop-pin c2, which enters a groove c3 in the seat, and thebar can move up with the member E until the pin brings up against theclosed upper end of the groove, which arrests further movement of thebar and consequently of the plunger member E.

The independent upward movement of the inner member F is limited in thefollowing way: In this member is formed an external vertical groove f,which affords clearanceway for a loose vertically-movable lifting-pin c,carried by the outer member E. For con` venience sake it is mounted inthe present instance in the locking-wedge e5, which locks the twomembers together at any desired point, as hereinafter described, thiswedge fitting the clearance-groove f in the inner member F. Upon theouter face and along one edge of the bar c is mounted a rod c7, so as tobe capable of limited independent vertical movement thereon, it beingconnected for this purpose with the barat suitable points by apin-and-slot connection, as indicated at e8. The rod at its upper endhas a head c, which overhangs the lifting-pin e, and at its lower end ithas a stud @10, which is beneath an angular extension G17 of the shelfor flange c16 on the downwardly spring-pressed valvelifting rod cl2. Thestud cw is so positioned that when the outer plunger member E hasreached its upward limit it (the stud) will be immediately under theangular extension c, as indicated in Fig. 1l. If, now, with the outermember E at rest, the inner plunger member F continues its upwardcourse, the movement will continue until the lower closed end of thegroove f meets the lifting-pin e6. Vhen this takes place, then anyfurther rise of the member F will raise the lifting-pin e6, which inturn will lift rod e7, with the effect of causing the latter through itsstud el@ to raise the valve-lifting rod cl2, thus opening theoil-discharge valve c11 and permitting any further oil-supply from thepump to return directly to the oil-reservoir without entering theplungercylinder. Under these circumstances further upward movement ofthe inner plunger mem mem F is of course impossible. The moment there issufficient escape of oil to permit the plunger the downward movement (avery slight movement) requisite to lower the stud 610, then thelifting-rod c12 will be depressed by its spring and the discharge-valvean will at once close and prevent further escape of oil.

I proceed now to a consideration of the means for locking the plunger inits adjusted position.

Each member of the telescopic plunger should be individually lockedthatis to say, the inner member should be locked to the outer member and theouter member should be locked to its cylinder; and it is also desirablethat these two locking devices should be so connected as to be operatedby one and the same handle, lever, or other instrumentality.

The neck of the jilunger-cylinder (this cylinder being, as shown, acasting made in one IOO with the base) is formed as a split ring, asshown in plan in Fig. 2, having ears D D2 and being divided for aportion of its periphery from the body of the casting by a horizontalslot or slit d. By drawing together the two ends or ears D D2 the ring-section formed by this slot or slit d' can be compressed most tightlyupon the outer plunger member E, which in this way is locked. The ear D'is rigid and has no movement. The ear D2 is upon and moves with themovable ring-section.

The drawing together of the ears, or, rather, the drawing of the ear D2toward the ear D', is effected by a cross-bar d2, which passes looselythrough both ears and has pivoted on one end a cam or eccentric d3,which bears against the outer face of the ear D2. By the action of thiscam and in accordance with the direction of its movement the ears willbe drawn together or allowed to separate, as the case may be. The camnormally is held in position to lock the ring upon the plunger by astout stiff spring d5, connected to the tail or stem d4 of the cam by astrap d6. The parts are shown in normal position in Fig. 9.

It is desirable, as before said, that the locking of the two plungermembers shall be occasioned by the movement of one and the same handleor lever. To this end I proceed as follows: Upon the outer face of thebar e is mounted a second bar a, the two being connected by links a', asindicated by dotted lines in Figs. 9 and lO, after the fashion of thetwo members of a parallel rule. Upon top of the bar e is placed thepivoted lever b, having one of its ends jointed tothe lockingwedge e5,as seen in Fig. 3, and its other end overhanging the top of the bar ce.Upward movement of the bar a will, by lifting the tail of the lever,cause its other end to depress the wedge e5 and jam it tight between thetwo members E F of the telescopic plunger, thus locking the two tightlytogether. A spring h normally holds the lever b in a position where thewedge is lifted and the member F is unlocked. The upward movement of bara for locking purposes is effected by the cross-bar cl2. Under thisarrangement the ear Dis a mere guide, through which one end of thecross-bar passes and in which it can move freely lengthwise. This end ofthe bar has on it a lateral offset or shoulder d?, Fig. 2, which abutsagainst the adjoining edge of the bar ci. When, therefore, the pivotedcam d3 is turned in locking direction, the first effect is to draw theshoulder d? of the cross-bar against the bar a, thus moving it.

cam d2 both members of the plunger are locked, the locking of the innermember taking place slightly in advance of that of the outer member. Itwill, of course, be understood that in its locking movement to the rightthe bar a does not travel far enough to meet or interfere with the rode7.

If desired, gibs or fiat pieces en (shown in dotted lines in Fig. 2) canbe set in the inner face of the outer tubular plunger member E at pointson a level with that at which the wedge e5 bears against the innerplunger member F, but on the side of the latter member opposite to thewedge. The plunger member F will, of course, be correspondingly shapedto fit against the flat faces of the gibs en. As the latter inclinetoward each other, forming approximately a V, the effect of forcing thelocking-wedge e5 home will be to jam the plunger member over into theV-recess formed by the gibs e, thus binding it tightly against rotation.

In order to lower the chair, I make use of the pivoted foot-lever G,Figs. 2, 9, 10, and 32. This lever, suitably journaled in the base, hasupon its axle an arm g for acting upon the tail of cam cl3 and aprojection g, which is designed to lift the valve-opening rod cl2, andfor this purpose extends under the shelf or flange o16, as indicatedmore plainly in Fig. 8, these two parts g g' being so arranged that thearm g will operate to unlock the plunger before the projection g acts toopen the valve. The lowering-lever G is depressed bythe foot of theoperator, and when that pressure is removed it is returned to normalposition by the spring d5.

Normally the plunger is locked, but when the chair is to be elevated itis then desirable that convenient means should be provided for unlockingthe plunger and holding it unlocked during the continuance of theelevating operation. To this end I connect the plunger-locking mechanismto the elevatinglever C2 in such manner that the act of adjusting theelevating-lever to its position of action shall cause the unlocking ofthe plunger and shall hold it unlocked so long as the elevating-levermaintains said position. The elevating-lever in this instance is made intwo parts joined together upon a vertical pivot C7, as shown clearly inFig. 2, so that when the lever is not in use its outer portion can befolded up or swung in toward the chairbase and thus be out of the way ofthe operator.` lIt is represented in this folded position in Fig. 9 andby dotted lines in Fig. 2. I avail myself of this construction toconveniently attain the end that I have in view. The outer section ofthe elevating-lever C2 is provided with an arm C4, which by a link C8 isjoined tothe tail or stem d4 of the cam d3.

The arrangement is such that when the le. ver is unfolded and inposition for use, as shown in Fig. 10 and in full lines in Fig. 2, thelink C8 will thereby be caused to turn the cam d3 in a direction torelease or unlock the IOO IIO

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plunger. Thus the plunger is automatically unlocked wheneverand so longas the elevating-lever is adjusted to its position of use. It will benoted that whether the lever is in either folded or unfolded positionthe joint C7 between the two sections of the elevatingleveris to oneside of a straight line between the points at which the link is attachedto the cani-tail d4 and the arm Ci, respectively, the arrangement beingsuch that whenever the outer lever-section is swung past the deadcenterin either direction it will be drawn and held in the position towardwhich it maybe moving at that time by the force ot the spring d5. Thelever will thus be held folded or unfolded, as the case may be, by thestress of the spring d5 and must be turned by the operator past thedead-center from either of those positions before it can by the act-ionof theispring be d awn to and held in the other position.

It is further to be noted that the link C8 is joined to the arm CLl byan eye C9, which permits the requisite lost motion to allow the link tomove freely on the arm without disturbing the elevating-lever when thecam d3 is operated by the lowering' foot-lever G.

To complete the description of the base it only remains to say that atthe point where the valve tripping or lifting rod c12 passes out throughthe top ot' the oil-chamber the opening through which it passes (whichmaybe used as the fillingoriiice) can readily be closed by means of acock or stopper 017, Fig. 8, mounted and movable up and down on the rod.This is a considerable convenience in packing the chair fortransportation. That portion of the base on which the orifice is locatedis formed as a pau cls, Fig. G, to catch any drip or leakage.

l proceed now to a description of the manner of and means for mounting`the chair-body upon the plunger, so that it may be tilted bothlengthwise and laterally to any desired angle and there secured.

The joint between the chair-body and the plunger may be described in ageneral way as a ball-and-socket joint-the ball carried by the plungerand the socket carried by the chair-body.

The ball is shown more particularlyin Fig. 9 at Il. lt is not a completesphere, but merely a segment formed by cutting ont' the spherehorizontally at top and bottom, so as to leave an intermediate segment.This segment is hollow and its top is closed or partly closed by a head71, Fig. l2. The plunger, or, rather, the inner member F of the plunger,passes up through this hollow spherical segment and is secured at itsupper end to the top or head 71. This arrangement gives very muchgreater vertical range of movement to the chair-bod y than otherwisewould be possible. As the ball is open on its under side, it

will pass over and surround the neck or upper part of the base when thechair is lowered, thus allowing the latter to descend until the head hbrings up or very nearly brings up against the base. Moreover, the ballon its rear side is cut away, as indicated at h', Fig. 12, this being toaltord room for the movement of the adjoining mechanism for thechair-back to be presently described.

It may here be noted that the plunger is se cured to the ball at a pointwhich laterally is to one side of the vertical axis or center of thelatter, as seen in Fig. 12. Thus the weight of the chair-body will bemore to one side of the plunger and consequently the tendency will be totilt the plunger toward that side with the eiiect of binding it in itsbearings, thus further insuring a rigid lock for the plunger at allpoints throughout its vertical range of movement. This feature isapplicable to any plunger, whether a telescopic plunger or a singlestemplunger.

The plunger is secured to the head h of the ball in anysuitable way-inthis instance bya split-ringand clamping-screw device, (shown at h4,Figs. 12 and 13.)

The socket which ts upon t-he hollowball segment is a socket dividedhorizontallyinto an uppe-r section l and a lower section I. The uppersection is carried by and secured to the spider-like arms j of thechair-seatframe casting J, Fig. l2. This section in dept-h is less thanhalf the ball, the partingline between the two sections l I' being ashort distance-say one-half inch or more or less-above the horizontalaxis of the ball.

The lower section l/ is divided vertically into two parts secured at therear to the chair seat frame at t', Fig. 12, and held to the uppersection by bolts or screws i', Figs. l2 and 14, passing into and throughears, with which both sections are provided at suitable intervals. Thislower section l forms in effect a split clamping-ring, its two freefront ends having ears i2, through which passes a suitable elampingscrew or rod t, by rotating which the ears will be drawn together orallowed to spread apart according to the direction of rotation of theclamping device. The rotation of the clam p in the direction to closethe ring upon the ball is effected by a crankhandle it, Figs. 1,12, and15,within convenient reach o'E the operator. It is when releasedautomatically pulled in the otherdirection to clamp the socket upon theball by means of a spring t5, Fig. 15. A very slight movement of thehandle @"1 serves to release the hold of the socket on the ball to allowthe rocking or tilting ot' the chair on its joint.

To prevent horizontal rotation of the socket on the ball, the socket isprovided with a stud t, Fig. lt-in this instance formed upon the innerface oi the lower section I', which enters and permanently engages avertical groove i7 in the exterior ofthe ball. This stud is radial andon the prolongation of the hori- IOO IIO

zontal axis of the ball crosswise of the chair,

.so that the chair-body can rock from front to rear without impediment,the stud occupying virtually the position of a pivot or journal, onwhich the rocking movement from front to rear takes place, whichposition it always maintains no matter what may be the extent to whichthe chair-body is tilted laterally.

Under the arrangement thusfar described whenever the socket is free tomove on the ball there is nothing to prevent the chairbody from rockinglaterally as well as from front to rear. Thelateral rocking movement isnot so frequently availed of as that from front to rear, and it is oftendesirable to hold the chair against lateral rocking while permitting itto rock from front to rear. To this end I form in the bottom of thegroove i7 a vertical series of holes t8, anyone of which is adapted tobe entered and engaged by a longitudinally-movable locking-pin t, thatpasses axially through the stud G and is inwardl y pressed by a spring10, held in a pocket i upon the lowersocket-section I. The stem of thislocking-pin passes out through the head of the pocket and is to beprovided with a suitable handle or other means for drawing the pin outfrom engagement with the hole in which it may happen to be.

It is desirable for convenience sake that the locking-pin should bemanipulated by the same instrumentality which operates the lower clamping socket-section I. To this end,

as shown in Fig. 15, I in the present instance provide the projectingouter end of the locking-pin stem with a projection or shoulder 12,between which and the pocket i extends one limb of an angle-lever 13,pivoted at its elbow to a bracket bearing on the socket-section I andhaving its other end'connected by a chain im or some equivalentinstrumentality to the crank -h'andle t4. The crank- 1 handle 4 willthus operate and control both locks or clamps for the socket; but, ashereinbefore stated, it is often desirable to opcrate the split-ringclamp which controls the rocking of the chair from front to rear without operating the lock which controls the lateral rocking. Theconnection t between the crank-handle i4 and the angle-lever 13 is madesufficiently slack for the handle to move far enough to open theclamping-ring l without affecting the angle lever. Further movement ofthe crank-handle beyond this point will operate the angle-lever also andwill leave the socket free to rock both laterally and from front to rearupon the ball. Suitable stops are of course to be provided for limitingthe tilting range of movement of the chairbody, as will be understood bythe skilled mechanic without further explanation.

To complete the description of this portion of the chair, it onlyremains to say that the ball can conveniently be provided with a bracketH, Fig. 9, for support of a spittoon or other attachment orappurtenance.

Foot-Board.

The main obj ect l have in view in this portion of my improvements is toprovide a footboard capable of a vertical adjustment independently ofthe seat-frame and maintained at all times practically in parallelismwith the seat, so that when raised to the level of the seat it willform, practically, an extension of the latter. My object in this is thatthe chair may be converted at will into what is tantamount to a couch.The adjustment is light and ready, owing to the fact that the foot-boardis balanced or very nearly balanced by a spring. The foot-board is alsocushioned for safety against sudden strain, as well as to prevent themovement of thc feet of the patient upon the board from shaking the bodyof the chair, this shaking being frequently a source of annoyance to theoperator in performing a delicate operation. The foot-board arrangementis represented more particularly in Figs. 1, 12, 113, 17, 17, and 1S.

The foot-board consists of the foot-board proper, K, and the Yfoot-boardframe.

The frame consists of two side arms or brackets L, cach hinged at l tothe under side of the seatfframe, and a screen L' of any ornamentaldesign, extending between said brackets. The frame can be swung up anddown upon its hinge Z and is held in its adjusted position by an ysuitable locking device. The locking device (shown more clearly in Figs.17 and 17l) consists in the present instance of a dog l, pivoted at l2to the foot-board frame and adapted to take into one side of the notchesin the under side of a rack-bar Z3, .fast to the seat-frame, the dogbeing normally held in engagement with the bar by a weight ZVL or itsequivalent.

I prefer to form the rack-bar with a horizontal laterally-projectingshelf Z5 and to provide the dog with a flange ZG, overhangin g theshelf, there being enough clearance between the flange and shelf toallow the dog to be disengaged from the notch in the rack-bar before theflange meets the shelf. The object of this arrangement is to provide astop against excessive movement of the dog. The iiange slides freely andeasily upon the shelf when the frame is being adjusted. There is one ofthese locking devices on each side of the chair, and the two dogs arerigidly connected by a cross rod or bar Z7, Fig. 17, so that they willmove always in unison. A handle Z8, Figs. 1 and 12, within convenientreach of the operator is provided for the purpose of manipulating thedogs. The foot-board proper, K, is hinged to the foot-board frame at 7c.It is provided on each side at its rear end with a downwardly-projectingear or lug k', with a cross-bar k2 extending between and pivoted IOO IIO

or journaled at its ends in said ears, the pivotal point being indicatedat 7a4, Figs. l and 17. To this cross-bar at about its center isfastened the lower end of the spring L for balancing the weight of thefoot-board structure. The upper end of this spring is made fast to a rodLG in line with the axis of movement Zof the foot-board frame.

On each side of the chair there is made fast to the cross-bar ki acontrolling-rod 797, the u pper end of which is pivoted at its to abracket 71;, secured to the seat-frame J. It is through thisinstrumentality that the parallelism of the foot-board K with thechair-seat is preserved. 'When the foot-board frame is swung up on itshinge l, it will be seen that therods 7c? will pull upon the ears 7c' ina direction to slightly turn the foot-board down, so as to compensatefor the upward tilt which otherwise would be given to the board.

The foot-board can be raised to the level of the chair-seat, preservingpractically its parallelism therewith: In this position the footboardframe will intervene to a slight extent between the chair-seat and thefoot-board proper, but this will be a matter of no moment. The body ofIthe patient will rest upon and be supported by the chair-seat, (and thechair-back as woll, which latter can also be turned back so as to be ona level with the chair-seat, if desired,) and the foot-board willsupport the legs of the patient without discomfort.

In order to cushion the foot-board for the purposes hereinbeforementioned, I interpose between the ends of the controlling-rods 707 andthe points on the cross-bar 7a4 to which the same are attached pads orcushions kw, of elastic material, such as vulcanized rubber, Fig. 1S,these pads being capable of yielding` to any sudden strain or jar uponthe foot-board proper, so as to prevent the movement due to this causefrom being apprcciably transmitted to the chair-body.

lith a view to permit the foot-board to be folded up against the body ofthe chair in compact form for transportation the joint k* between thecross-bar k2 and the ears 71; is made by forming the cross-bar at itsends with half-round bearings, as in Figs. 17 and 18, which rest uponpins or journals projecting inwardly from the interior opposite faces ofthe ears 7c. Under this arrangement the foot-board can, by hand, bemoved to disengage the journal-pins from the half-round bearings in thecross-bar, and can then be folded up independently of the cross-bar. Toprevent the cross-bar k2 when thus released from being pulled up by thespring 7c, I form the parts k7 and L vary their positions relatively toeach other during the adjustment of the foot-board, and they also holdthe crossbar 7a2 always in such position that when the foot-board isturned down again from its folded position the journal-pins on the ears7V" will enter their half-round bearings on the under side of thecross-bar.

At the front of the foot-board is a foot-rest Kl, carried by a supportK2, which is essentially a crank-arm swiveled upon a vertical axis in asocket 7c in the foot-board. The object of this arrangement is that thefootrest may be brought nearer to or farther from the chair-seat, as theconvenience of the patient may require. On the front and rear of thesocket 7s are diametrieally opposite notches 7tlg, one or the other ofwhich will be engaged by the pivoted detent-lever 7tlg. This lever isweighted or spring-pressed, so as to automatically engage the notchopposite which it may be brought; and its handle end is convenientlyplaced so that it may be reached and manipulated by the operator at thetime he takes hold of the foot-rest for the purpose of reversing itsposition, or it may, indeed, be operated by the patient, using merelythe foot for that purpose. I am aware that a reversible foot-rest is notnew, broadly considered, but I believe the arrangement for that purposejust described to be new with me.

Auxiliary Siep.

In high-low chairs an auxiliary step by means of which when thechair-bodyis raised the patient can get up into the chair is animportant adjunct; but any such step which comes between the foot-boardand the floor on which the chair stands will necessarily limit theextent to which the chair can bc lowered unless it be so arranged thatit can fold up when occasion requires, so as to allow the chair to bclowered even to the point where the foot-board is practically in contactwith the floor, as at times is necessary. With this in view I havecombined with the footboard what I term an au tomatically-adj ustablestep, which, when the chair is raised, will be automatically unfolded orprojected into position for use, as well as braced in that position, andwhich, on the other hand, when the chair-body in its descent reaches aposition where the step brings up against the floor, will, when thechair descends farther, automatically fold up, so as to permit thatdescent to be unimpeded. The manner in which I attain this result willbe understood by reference to Figs. 1, 1Q, and 1G, the iigure last namedbeing a section on line 1G 16 of Fig. 12.

The step proper, M, which is below the footboard K, is intended toproject laterally beyond the latter, as indicated in Fig. 12. It is heldbetween the forked outer end of a supporting-arm m, connected to theunder side of thc foot-board by straps m. The arm IOO IIO

is hung between and pivoted at about its middle to t-he lower ends ofthese straps, as shown at m2, Figs. 1 and 16, and the straps at theirupper ends are hinged at m3 to the under side of the foot-boord near oneof itsedges. The arm m back of its pivot is extended to form a brace,the upper end of which is adapted to take into a notch m4 in an abutmenton the under side of the foot-board. In this position it will be seenthat the step is thoroughly braced to sustain the weight of the personstepping upon it. It is brought to this position by the action of aspringm, coiled upon the pivot m2 and bearing outwardly at its endsagainst the straps m'. This spring is put under compression when thestep is folded up and by its stress tends to cause the step to resumeits unfolded position. (Shown in Fig. 1G.)

Under the arrangement shown when the chair has descended far enough forthe step to reach and bear against the floor then further descent of thechair-body will cause the step to fold up toward the straps m, thelatter swinging inward at the same time until when the chair-bodyhasdescended far enough the step as a whole will be folded up iiat againstthe bottom of the foot-board, as indicated by dotted lines in Fig. 16.On the step supporting arm m l mount idlers or friction-rollers whichwill ease the folding movement of the step and prevent the friction anddrag between the arm m and the floor surface which otherwise would takeplace. The moment the chair is raised far enough the step will resumeits unfolded position. (Shown in full lines in Fig. 16.)

l remark here that the spring may be dispensed with and the frame can beso weighted or made so heavy as to automatically unfold by gravity whenpermitted to do so, and I desire to be understood as including any suchobvious modification or substitution in my claims.

Arm-Rest.

My invention in this direction contemplates combining with the chair anarm-rest which at the lower end of its support is pivoted to theseat-frame in such manner that when desired the arm-rest can be turnedupon its pivot forward and down alongside of the footboard, a suitablelock bein gprovided for holding it rigid when in its normal position.The object is to provide an arm-rest which when occasion demands may bebrought to a position in which it is entirely out of the way of theoperator. This portion of my invention is illustrated in Figs. 1, 12,19, 30, and 31.

The arm-rest is shown atNand its support at N. The support at its lowerend is pivoted at 'n to the seat-frame, at or near the forward end ofthe latter, on a horizontal axis, which will permit it to be swungforward and down, as indicated by dotted lines in Fig. 19. In thisposition it is alongside of the operator and entirely out of his way. A

stop n on the support is provided to limit the extent to which the armcan be turned down. This stop, when the proper limit is reached, meets ashoulder or abutment n2 on the seatframe and prevents further movementin that direction.

The arm-rest when raised and innormal position can be rigidly locked inthat position by any suitable means-in this instance by a cam-lever n3,Figs. 12 and 19, pivoted to the seat-frame, havinga cam end to bearagainst a proper vabutin ent n* on the arm-rest support N and a handleend by which it is operated.

By depressing the handle end the cam end of the lever will be jammed andwedged against the abutment n4, thus rigidly locking the arm-rest inposition. By lifting the handle end of the lever the arm-rest will bereleased.

The hinge or pivot point n of the support N' is at a point considerablybelow the seat and at or near the front end of the seat-fram e, thusallowing the arm-rest to swing forward and down, so as to practically beclear of the side of the chair. Then the arm-rest is raised intoposition, its support N rests by gravity upon the rail on the side ofthe seat-frame Iwhere the cam-lever n3 is located, and this leverengages the support at a point above the hinge n and between the latterand the arm cushion or rest proper, N. Thus the armrest, when raisedinto position, always stops in the right place and can be most firmlylocked in that position.

It may be desirable at times to entirely remove the arm-rest from thechair. A convenient arrangement to permit this is illustrated in Figs.30 and 31. The cylindrical pivot-stud n, attached to the arm-restsupport N', enters a suitable socket or bearing formed for it in theseat-frame J and is peripherally grooved at h5 to receive a cross-pinns, which holds it in its bearing without impeding its free rotationtherein. The stud on one side is. cut away back of this groove, as shownat n?, so that when it is turned far enough to bring this cut-awayportion opposite the pin n the latter will no longer engage the stud,and the latter can then be withdrawn from its socket in the seat-frame.The parts are shown in Fig. 30 in the position which they occupy whenthe arm-rest is raised and in normal position. Vhen the arm-rest isswung forward and down, as in dotted lines in Fig. 19, the cut-away partn.7 of the pivot-stud n will. be brought opposite to the cross-pin n,and the arm-rest is then free to be removed from the chair.

The Back.

The back of a dental chair generally consists of a back-supporting framehinged to the seat-frame so as to be inclined from front to rearrelatively to the seat, in combination with a back proper carried by andvertically adjustable upon the back-supporting frame. Usually theback-supportin g frame is hinged IOO to the seat-frame by pivots held insuitable bracket supports. These pivots and their supports unduly limitthe range of vertical movement of the back proper, preventing the latterfrom being lowered as far as it otherwise might be, and are also in theway of the operator. To obviate these objections, I imite theback-supporting frame to the scatframe by arc-shaped concentrichinge-pieces, the one moving in or upon the other and a lock beingprovided to hold the parts in their adjusted position. I have alsoimproved the construction and arrangement of the parts which compose theback proper. This portion of myimprovements is illustrated in Figs. 1,12, 13, 2() to 27, inclusive, and 29.

The arc-shaped hinge member which is carried bythe seatframe is shown atO, Figs. 1, 12, and 13. It has the shape of an inverted trough and isfastened concave side uppermost to the rear of the seat-frame, below thetop of the same, with its inner end projecting up under the seat-frame,as seen in Fig. 13. On each oi' its interior opposite side walls it hasa tongue o, curved longitudinally in the arc ot a circle, to engage acorresponding groove in the back-supporting frame, and it is furtherprovided with a rack or series of teeth o in the under Jface of its topto receive and engage a locking-dog carried by the backsupporting frame.

The back-supporting frame consists of4 two guide-rails P, straight forthe greater portion of their length, but at their lower ends curved inthe arc ot' a circle corresponding to that of the arc-shaped hingemember O, these curved lower ends being connected on the side or facenext to the seat-frame by a web I, which runs under thecorrespondingly-curved top of the hinge member C). In the exterioropposite faces of the curved ends of the rails P are curved grooves p,into which the tongues o are received when the two concentric hingemembers are fitted together. Under this arrangement the hinge isentirely out of the way of the operator, and as it is below the seat itallows the back to descend until, if need be, the lower end of theback-pad will come between the seat and the back-supporting frame.

As the hinge members are placed concave side uppermost, the tendencywhen the back is inclined rearwardly is to close any interval betweenthe back-pad and the seat. Moreover, the extended contact bet-ween thetwo hinge members produces friction,\vliich tends to prevent sudden dropof the back-supporting frame when the latter is unlocked. To increasethis frictional resistance, I provide the back-supportin g frame with afriction-pad p', Figs. 20, 2l, and 29, which projects through one of thegrooves p in position to bear upon the tongue o of the hinge mem-ber Oand for this purpose is outwardly spring-pressed by a coil-spring p2,surrounding the stem of the pad and coniined between the head oi thelatter and an abutment p3 on the web P' of the back-supporting frame.

The lookin g together of the hinge members is e'ltected by the tootheddog p4, pivoted to the under side of the web P, with its toothed endprojecting through an aperture in the web in position to engage the racko, as seen in Figs. 21 and 13, the toothed end of the dog beingoutwardly pressed for this purpose by a spring' p5. For the purpose ofunlocking the dog I provide a handle p, mounted upon the upper part ofthe chair-supporting frame, my object in thus locating the handle beingto permit the operator to use the same handle by which he unlocks theback-supporting frame to uphold that frame also. The handle p thuslocated can be connected to the locking-dog by various devices whichwill suggest themselves to the skilled mechanic.

The mechanism which I now prefer for this purpose and which is shown inFigs. 20, 21, and consists of an arm p7, iixcd to the axle p8, to whichthe dog also is fixed, and a connecting-rod p9, jointed at its lower endto the arm p7 and at its upper end to a crank p10 on the stem or arborof handle jf. The connecting-rod is housed in one of the rails P, whichis suitably formed for this purpose.

I am aware that a hinge consisting of two concentric arc shaped membersfitted together and adapted to slide the one on or in the other is notnew and has been used for various purposes; but I am not aware that sucha hinge has ever before been applied and used in the manner hereinbeforedescribed to connect a seat-frame and a backsupporting frame whetherprovided or not with a back vertically adjustable thereon. The locationof the unlocking-handle on a position on the back-supporting frame topermit the operator to use the same handle at once for unlocking theframe and supporting it at the same time I also believe to be new withme.

I proceed now to a description of the Vertically-adjustable back. Thisback consists of a back-pad Q and a carrier R therefor. The carrier R isa skeleton frame which fits between the rails P of the back-supportingframe and is held in ways therein in which it can move up and down, Iprefer to form on the interior opposite faces of the rails longitudinaltongiiesp,Figs. 12 and Z4-,which enter and engage corresponding groovesin the exterior opposite edges of the carrier R. I prefer that thesetongues and grooves should have a dovetail formation, as indicated inthe figures referred to, so that the carrier may serve to hold togetherthe upper unconnected ends of the railsP and prevent any tendency ontheir part to spread apart, the undercut forming the dovetail beingpreferably ou one side only of the tongue and that side the front sideor the side next to the back-pad. The back-pad carrier R can move freelyup and down between the rails P, the extent of IIO joining the bar.

its downward movement being limited by stops p12, Fig. 20, against whichbrings up the cross-bar r on the carrier R. This cross-bar I utilize asa clamp to fasten the carrier R in its adj usted position. Thecross-bar,as shown in Fig. 23, is a loose bar, and at the point where itis located the carrier is cut away so as to expose the sides of thetongues p11 ad- Thus the tongues p11 at this point are embraced betweenthe carrier on one side and the clamp-bar r on the other.

The clamp-bar is controlled by a knob or handle r', which screws upon ascrew 0'2, passing loosely through the clamp r, and is fixed rigidly tothe carrier, as shown in Fig. 23. By screwingthe handle down upon thecrossbar the latter will be forced up against the tongues p, and thelatter will thus be tightly bound and clamped between the cross-barclamp on one side and the body of the carrier R on the other. X'Vith aview to still eX- ert upon the carrier R, even when the latter isreleased, a frictional contact of the clamp r, which will prevent suddendrop of the carrier, I provide a spring r3, held in a socket in theclamp and confined between the latter and the inner end of the handler'. This spring, which is strongly compressed when the handle is screwedhome, tends when the handle is turned in a direction to release thecarrier to cause the clamp to still exert pressure sufficient to preventtoo free movement of the carrier R.

The back-pad Q is hinged at its upper end upon a horizontal axis to itscarrier R, so that it may be tilted or inclined from front to rear uponthat hinge as an axis. The hinging of the two together is effected inthis instance by blocks q, having pivot-pins q, mounted in bearings orbosses q2 in the'backp'ad frame Q', as illustrated more particularly inFigs. 22 and 26, the blocks t7 being fastened to the carrier R by screwsr1", Figs. 20 and 2G. Thus while all parts of the hingejoint are coveredby the upholstery of the back-pad, yet the pad can at any time bereadily removed simply by taking out the screws r4.

The frame Q is a suitable skeleton frame of some appropriate materialupon which as a foundation the pad is upholstered. The pad Q is held inits adjusted position relatively to the carrier by a pivoted latch ordetentr on the carrier, Figs. 2l and 27,which engages a rack or notchedbar g3, the inner end 'of which is made fast to and contained in apocket g4 in the back or rear face of the pad, this pocket being forreception of the dog when the pad is folded up against the carrier. Toprevent the backpad from being swung out far enough to disengage itsrack Q3 from the detent 915, the rack has on its outer end alaterally-projecting stop Q5, which. is in the path of a :finger r6 onthe detent., Figs. 13, 2l, and 27. Vhen the back-pad has been swung outaway from its carrier a certain distance, the iinger r6 will bring upagainst the stop g5, thus preventing further movement of the back-pad inthat direction. The detent T5 drops by gravity into engagement with therack, but a spring may be used to insure the engaging action. ifdesired. By a handle rl, Fig. 27, with which the detent is provided, thelatter can be lifted by hand so as to be disengaged from the rack g3.

T he Head-Rest.

The head-rest mechanism which I am about to describe is verticallyadjustable and capable also of permitting the head-rest pad all themovements of the human head and all of its various joints simultaneouslylocked or unlocked, as the case may be, by the operation of a singlehandle. It is illustrated more particularly in Figs. l, 1S, 20, 2l, 21,24, 2G, and 2S.

The head-rest carrier is a jointed stem coinposed of three sections S SS2, united together by universal joints. The lowermost section S, whichis tubular or hollow, is mounted and adapted to slide up and down on adovetailed way frs, Figs. 20, 2l, 2t, and 2G, provided for it on theback-pad carrier R, the section S, as indicated in Fig. 2li, beingformed with a base grooved to fit upon and embrace the dovetailed wayfrs. It will be noted that this way is inclined from front to rear withrespect to the back-su pportin g frame Rin which the .carrier R moves,its inclination being to the front at its upper end. The inclination issuch in fact as to cause the upper portion of the way r3 to be received,as it were, within the compass of the back-pad Q, the upper portion ofthe rear face of which, except at the point where it is intended toaccommodate the way rs, being in rear of the way when the back-pad isfolded up against the carrier R and its hinge being the rear of the wayrs. The object of this formation is to give a greater range of forwardmovement to the head-rest stem, in order to bring the headrest padfarther to the front than otherwise would be practicable.

To the uppermost section S2 is attached the head-rest proper, T. Theintermediate section S is connected to its two fellow sections byball-and-socket joints. The uppermost section Siis solid and has a ballson its lower end. The middle section S has a ball .S2 on its lower endand at its upper end has a socket to receive the ball s of section S2.This socket is formed bythe concave upper end of section S', inconjunction with a sleeve s', which screws upon the section and hasaconcave interior shaped to iit upon the ball s. In both theball-and-socket ends of the intermediate section S' are formed pocketsto receive pressers s3, and the section between these sockets islongitudinally bored to receive a spindle s4, which extends between andcontacts at its ends with the pressers s3. These pressers project alittle beyond their pockets into the sockets to which they respectivelypertain.

The ball s2 on the lower end of the middle IOO IIC

section S is held in a socket formed by the sleeve S5 screwing upon theupper end of the lowermost section S, in conjunction with the concaveupper end of the push piece s6, mounted and longitudinally movable insection S. Under this arrangement when the push-piece s6 is forced up itwill jam the ball s2 of the middle section S tight in its socket and atthe same time will, through the lower presser S3 and spindle si, causethe upper presser s3 in a similar manner to jam the ball s of the topsection S2 tight in its socket. Thus by upward movement of thepush-piece s both joints of the head-rest stem will be locked rigidly,and, correspondingly, when the push-piece s6 is allowed to drop bothjoints will simultaneously be'unlocked. Manifestly various means can beemployed to thus actuate the push-piece. The device which I now preferfor the purpose consists of the toggle-lever S7, provided with a spring3S, by which the toggle is kept normally bent. This toggle-lever isplaced in the section S in the position shown in Fig. 21, with its endsbearing at the top against the push-piece s6 and at the bottom againstan abutment S9 on the interior of the section. A pressure-screw S10,provided with an external operating handle or knob s, enters the sectionthrough a suitable screw threaded socket in a position where its innerend will bear against the toggle-lever. By screwing in thepressure-screw it will straighten the lever, with the effect of forcingup the push-piece s and thus locking both joints. IV hen thetoggle-lever is relieved from the pressure of the screw, it will resumeits normal bent condition and the joints will unlock by gravity.

I'Vhile other means may be employed to lock the head-rest stem againstvertical movement upon the way T8, yet it is very much to be preferredthat this locking action should be effected by the same instrumentalitywhich locks the joints between the sections of the stem. This result isattained by the mechanism just described. The toggle-lever at its lowerend is seated in the angle at the junction or meeting-point of theabutment 39 and the face of the way frs and bears against. both. Thentherefore the toggle-lever is straightened by the action of thepressure-screw, its lower end will be jammed not only against theabutment, but also with equal force upon the face of the way, and thesection S in this way will be rigidly clamped or locked to the way rs bythe same movement of the same instrumentality which locks the jointsbetween the sections of the head-rest stem. This feature I believe to benew with me beyond its particular embodiment represented in the drawingsand just described.

Manifestly other means besides the togglelever can be employed. I mightuse, for example, the arrangement illustrated in Fig. 33, in which theinstrumentality which operates upon the push-piece s is a lever S12,pivoted in the section S and provided with an offset or projection whichcomes under and is adapted to lift the push-piece. The free end of thelever has a screw-threaded boss engaged by a pressure-screw S15, which,passing loosely through the section S, screws into and through the bosswith its inner end contiguous to the face of the way rs. A stiff spring314, encircling the stem of the screw, is interposed between the lever312 and the shell or case of section S. By turning the screw in theproper direction the free end of the lever will be caused to travel uponit in a direction to lift th e push-piece and consequently to lock thejoints between the sections of the stem. At the same time this travel ofthe free end of the lever will have the effect of jamming the inner endof the screw against the face of the way with sufficient force to clampthe stem securely thereto. When the screw is turned in the oppositedirection, the spring s14 tends to move the lever S12 from actionagainst the push-piece.

The head-rest proper, Figs. 20, 21, and 2S, consists of a pair of padsT, adj ustably mounted upon a bracket t, fast to the upper stemsectionS2. One pad is held to its bracketarm by a clamping-screw t', whichpasses through a longitudinal slot t2 in t-he arm. The other pad is heldto the other bracket by means of a split ring 3, to which the pad isfastened, this ring encircling and being adapted to rotate upon a hubt1, carried by the bracket-arm. A clamp-screw t5 serves to hold thesplit ring in its adjusted position. In this way I can regulate withease the distance between the adjoining ends of the two pads, as well asthe angle at which the pads are to stand relatively to one another.

I-Iaving described the best way now known to me of carrying myimprovements into effect, I state, in conclusion, that I do not restrictmyself to the particular mechanical details hereinbefore set forth andillustrated in the accompan ying drawings, for manifestly the same inmany respects can be widely varied without departure from the spirit ofmy invention; but

What I claim herein as new, and desire to secure by Let-ters Patent, isas follows:

I. The combination with the plunger-cylinder and plunger, the pump andthe duct leading from the pump to the cylinder, of a pressurestorage-chamber interposed between the pump and cylinder, andcommunicating with said duct, a movable head or diaphragm in saidchamber, and a sprin which presses said diaphragm in a directionopposite to that in which it is forced by the liquid on its Way from thepump to the cylinder, substantially as and forthe purposes hereinbeforeset forth.

2. The combination with the base and the plunger-cylinder, of the pumpand pipe connections between it and the cylinder, together with thecontrolling-valves therein, formed as one structure dctachably connectedto the IDO IIO

